Electrically and frictionally derived mound temperatures in carbon graphite brushes

Abstract

Thermal mounding in brushes can cause concentrations of electrical and mechanical loading. Joule heating due to current constriction and plastic work dissipation associated with sliding friction give rise to very intense subsurface heat sources local to the thermal mound. Coupled with the nonlinear material thermal properties of brush grade carbon graphites, temperatures of thousands of degrees Celsius can result. Numerical and analytical simulations of mound temperatures are presented as the mound evolves from cold to hot. The temperature field about a thermal mound in an electrical brush is estimated using a heat conduction equation with frictional and electrical internal heat sources. Properties vary realistically with temperature, and variations due to changes in current, sliding speed, and other factors are also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>